EK129

The steel remains elastic while in linear range, and recovers perfectly on unloading. The limit of the linear elastic behaviour is often closely approximated by the yield stress. Beyond this limit the steel flows plastically without any increase in stress until the strain-hardening strain is reached. This plastic range is usually considerable, and accounts for the ductility of the steel. The stress increases above the yield stress when the strain-hardening strain is exceeded, and this continues until the ultimate tensile stress is reached. After this, large local reductions in the cross-section occur, and the load capacity decreases until tensile fracture takes place.